fix(books): 泥潭策展语与回退契约实现；自托管仓星标语义

- BooksPage 实现 schema 注释承诺的 description 回退（正文首段去记号
  取 60 字）——视觉复核抓到的"文档说了代码没做"缺口
- 泥潭补人工策展语（回退之上）；自托管仓星标改 self-hosted 徽标
  （gitea 无 star 真值，★0 语义突兀——视觉复核次要备注）

验证: build 28 页 exit 0；dist/books 含泥潭策展语；dist/opensource
      self-hosted 徽标与 ★57 并存实测

Spec: 2026-10-25_add-terminal-books-admin

Co-authored-by: GLM-5.3

src/components/geek/ProjectWall.astro

@@ -39,7 +39,7 @@ try {
                 {p.language}
               </span>
             )}
-            <span class="stars">★ {p.stars}</span>
+            <span class="stars">{p.source === 'gitea' ? 'self-hosted' : `★ ${p.stars}`}</span>
           </span>
         </a>
       </li>

src/components/pages/BooksPage.astro

@@ -12,6 +12,12 @@ const { locale = 'zh' } = Astro.props;
 const books = (await getCollection('posts', ({ data }) => !data.draft && data.category === 'reading' && !data.tags.includes('hidden')))
   .sort((a, b) => b.data.pubDate.valueOf() - a.data.pubDate.valueOf());
 
+// 回退契约（schema 注释声称而此前未实现——视觉复核抓到的缺口）：
+// description 缺省取正文第一个非空段落（去 markdown 记号）前 60 字
+const firstPara = (body: string | undefined): string => {
+  const line = (body ?? '').split(/\n\s*\n/).map((l) => l.trim()).find((l) => l && !l.startsWith('#') && !l.startsWith('---')) ?? '';
+  return line.replace(/[*_>`\[\]]/g, '').slice(0, 60);
+};
 const years = [...new Set(books.map((b) => b.data.pubDate.getFullYear()))].sort((a, b) => b - a);
 const L = {
   shelf: locale === 'zh' ? '书架' : 'Books',
@@ -36,7 +42,9 @@ const L = {
               <div class="bk-body">
                 <strong class="bk-title">{b.data.title}</strong>
                 {b.data.bookAuthor && <span class="bk-author">{b.data.bookAuthor}</span>}
-                {b.data.description && <span class="bk-desc">{b.data.description}</span>}
+                {(b.data.description || firstPara(b.body)) && (
+                  <span class="bk-desc">{b.data.description ?? firstPara(b.body)}</span>
+                )}
               </div>
             </a>
           </li>